1. Field of the Invention
The invention lies within the art of designing a composite armor plate. The invention also lies within the art of signal processing as used in conjunction with nondestructive testing.
2. Background Art
One aspect of the invention relates to nondestructive testing of manufactured articles or other work pieces of interest. A common form of nondestructive testing is subjecting a work piece to vibrations at selected amplitudes and frequencies and thereafter analyzing the vibrational responses of the work piece. Typically transducers on the work piece transmit signals or signal patterns that are processed by a computer algorithm or by logic circuitry to determine whether the work piece is flawed. A relatively early example, circa 1958, of this sort of nondestructive testing is U.S. Pat. No. 3,023,609 to Schubring. Often in nondestructive testing, work pieces known to be flawless or at least acceptable are tested in order to establish a standard or baseline against which subsequent test results for later-produced work pieces can be compared. For example, see U.S. Pat. No. 5,195,046 to Girardi et al.
Numerous data analysis techniques historically have been used to process data that is derived from sensor output signals in nondestructive testing. A comprehensive treatment of data analysis techniques is found in Handbook of Data Analysis by Alan Bryman and Melissa A. Hardy published in 2004 by SAGE Publications Ltd, this book being available on line at http://books.google.com/books. Aside from Gerardi, there are innumerable other examples where acoustic or vibrational nondestructive testing is performed on work pieces using well-known data analysis methods. One example is U.S. Pat. No. 7,076,695 to McGee et al. The data analyzing techniques in McGee include, inter alia, a Chi-square test, elimination of non significant data, normalization, and centering of data. The McGee methods are adaptable to production environments or post production testing of manufactured items during the items' lifetime. Application of acoustic or vibrational non destructive testing techniques to a plate of composite armor and the use data analysis to interpret vibrational responses of the plate has been shown and discussed in the article “Damage Detection in Composite Plate Armor Using Ultrasonic Techniques” by Meitzler et al released Aug. 17, 2009 and available on line at http://oai.dtic.mil.
Another aspect of the invention relates to the structure composite armor generally and relates particularly to composite armor having at least one layer comprised of ceramic tiles. An overview of various composite armor structures is seen in “Repair of Composite Integral Armor by J. W. Gillespie, Jr. presented at the NCMS CMTA Symposium at Jacksonville, Fla., Apr. 16-18, 2002. This and other references show at least one layer in a composite armor plate comprised of closely spaced ceramic tiles. Many on-line sites discuss composite armor structures. By way of example these sites include a discussion of Chobham armor at http://en.wikipedia.org/wiki/Chobham_armor and a commercial site http://www.rankarmor.com/no_vehicle.php. See also U.S. Pat. No. 5,790,843 to Strasser et al., which shows various ballistically protective materials used in an integrated armor plate structure.
A further aspect of the invention relates to the use of piezoelectric transducers in composite armor structure. The aforementioned article, “Damage Detection in Composite Plate Armor Using Ultrasonic Techniques” shows the use of piezoelectric sensors with a ceramic composite armor plate. Ceramic piezoelectric sensors with customized geometries can be obtained from commercial sources. See, e.g., the Omega Piezo Technologies web site at http://www.omegapiezo.comiceramic_components.html.